OBJECTIVE: To investigate the effect of a vacuum-assisted socket suspension system as compared with pin suspension on lower extremity amputees. DESIGN: Randomized crossover with 3-week acclimation. SETTING: Household, community, and laboratory environments. PARTICIPANTS: Unilateral, transtibial amputees (n = 20 enrolled, n = 5 completed). INTERVENTIONS: (1) Total surface-bearing socket with a vacuum-assisted suspension system (VASS), and (2) modified patellar tendon-bearing socket with a pin lock suspension system. MAIN OUTCOME MEASURES: Activity level, residual limb volume before and after a 30-minute treadmill walk, residual limb pistoning, and Prosthesis Evaluation Questionnaire. RESULTS: Activity levels were significantly lower while wearing the vacuum-assisted socket suspension system than the pin suspension (p = 0.0056; 38,000 +/- 9,000 steps per 2 wk versus 73,000 +/- 18,000 steps per 2 wk, respectively). Residual limb pistoning was significantly less while wearing the vacuum-assisted socket suspension system than the pin suspension (p = 0.0021; 1 +/- 3 mm versus 6 +/- 4 mm, respectively). Treadmill walking had no effect on residual limb volume. In general, participants ranked their residual limb health higher, were less frustrated, and claimed it was easier to ambulate while wearing a pin suspension compared with the VASS. CONCLUSIONS: The VASS resulted in a better fitting socket as measured by limb movement relative to the prosthetic socket (pistoning), although the clinical relevance of the small but statistically significant difference is difficult to discern. Treadmill walking had no effect, suggesting that a skilled prosthetist can control for daily limb volume fluctuations by using conventional, nonvacuum systems. Participants took approximately half as many steps while wearing the VASS which, when coupled with their subjective responses, suggests a preference for the pin suspension system.

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